Electric sound-reproducing device



Nov. 17,1925. I 1,561,825

0. BOTHE ET AL ELECTRId SOUND REPRODUCING DEVICE Filed Jun 6, 1924 011k: @dib Patented Nov. 17, 1925.

UNITED STATES or'ro rerun, or s'rnom'rz, nan

BEBEZIN, AND L'UDWIG SCHIFF, 0F BERLIN, GERMANY.

ELECTRIC SOUND-BEPBODUGING DEVICE.

application filed June S,

To all whom it may comm.

Be it known that we, Or'ro Bo'rHn, residing at Steglitz, near Berlin, Germany, and Lunwic Somr'r, residing at Berlin, Germany, have invented certain new and useful Improvements in Electric Sound-Re roducing Devices; and we do hereby dec are the following to be a full, clear, and exact de-' scription of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings and to letters or ii of reference marke thereon, which form a part of this specification. y

This invention relates to electrical devices for reproducing sound and particularly to devices of this kind adapted for use in acoustical cinematography (speaking films) and in the electrical transmission to a dis tance of concerts, speeches, lectures or the like without distortion of the original sounds and without extraneous noises. To accomplish this a fluid current such as a current of gas, air or steam by whose pressure fluctuations sound waves of any desired strength can be produced, is employed. This invention diflers rrom known devices of this kind in that the acoustical control of the fluid current used for the production of sound is not performed b a mechanical valve which has inertia, but by aurely electrical agency in the form of an e ectric field, the fluid current being electricall charged for the contemplated pu se. e invention enables a pure repr notion of original sounds to be obtained, extraneous sounds and changes oft'imbre being avoided because all influences that tend to falsify the characteristics of the o al soimd, such as eddies, disturbing nature irequencies, damping and cuttin out of high harmonics by mechanical, e ectrical or magnetic inertia, are elimi nated. Hence all sounds, even the most com Heated ones, can be quite faithfull re prodhced, even when they are amplified far beyond their natural loudness in order to make them audible to a very large audience. A fluid in the form of gas or steam can be charged with electricity in diflerent ways. Air for exam le can be ionized in a known manner by ultraviolet light, Rdntgen rays,

radioactive substances, heating to a high temperature etc. A particularly simple and efl'ective electrifying means for steam is 1924. Serial No. 718,3

an Armstrong steam electrifying machine adapted for the purposes contemplated by this invention. 7

The production of an electric field by talking currents (by which, in this specification, is meant electric currents in general whose fluctuations of strength and potential correspond to the rhythm of the sounds to be reproduced) maybe efi'ected by causing the talking currents, which may be amplified by one or more thermionic valves 'or suitable amplifiers, to charge a perforated metallic bq y'such as a sieve, grid or the like. The electrically char ed fluid is controlled by being conducted through the perforated me tallic bod The tafin'ng currents which produce the said electrical field may be produced by a device located near the sound producer or combined therewith, as for example with the aid of a plastic phonogram (phonographic record) which controls one or both of the electrodes of an electric discharge gap or an electrode placed between the two electrodes of a discharge gap.

The invention is illustrated by way of example in the drawing, in which 1 is the boiler of an Armstrong steam electrifying machine, and 2 designates electrical heating elements placed in the interior of the water container. The heatin elements 2 are heated by a current whic is regulated by an automatic device hereinafter more fully described so that the steam pressure is always maintained constant. The steam produced is conducted through a. short pipe connector 3 into a condensing vessel 4 provided with cooling rips, the steam being thus caused to travel past the condensed water 5 that .forms in the vessel. It is thus saturated with water bubbles. This moist steam is conducted thence through a nozzle 6 and a very narrow serpentine channel 7 formed in a. bod 7 that is referably made of box wood. uring their passage through the channel 7 the particles of water carried along by the steam are positivel charged by their friction with the Walls 0 the channel. To increase the friction the inside width of the channel is small and the channel has a serpentine form so as to cause the steam to continually change its direction of flow and to thus force it to brush against the channel walls. The 0- larity of the steam can be reversed by makm it' pass over oil, for example turpentine oi llil . between the inlet nozzle 6 and the exit nozzle 8 also has the effect of causing the steam to flow out without the formation of eddies therein so that disturbing collateral noises (hissing or swashing) are obviated. At the front end ofthe exit nozzle 8 there is a perforated metal body or grid 9 which is electricall charged as hereinafter described y currents. so that the intensity of the electrical char e of the grid fluctuates in the rhythm of the sound waves to' be reproduced. The steam issuing from the grid 9 flows through a trumpet 10 which forms a continuation of the path through the grid.

From the trumpet steam passes into the external air. The shape of the trumpet 10 is such that condensed water may collect at its lowest part. This water may be conducted back to the boiler 1 from time to time, this operation being performed manually or antomatically by a device. (not shown) provided for this purpose. i

The sound reproduction device operates in the following manner: 'The electric field or intensity of the charge of the metal grid 9 is proportional at every moment to the potential connected to the grid. If, as shown in the drawing, the potential connected to the 'd is pos ive, the steam will be repelled before and behind the griddueto the positive'charge of the small water bubbles in the steam. The magnitude of the repelling forces fluctuates in accordance with the in-. tensity of the electric field or the strength of the potential applied. Consequently the amount of steam that passes through the sieve will not remainfcimstant but. it will be subjectedto fluctuations of pressure that will become noticeable in the exterior. air in th form of sound waves.

In. the device shown in the plastic phonogram impressed on the sound record or film 11 is used for the'production of talkin curren-ts'in the following manner: A feeler is kept pressed by a spring against the film 11 which is moved continuously by a feed roller 12. The feeler 13 carries a grid-shaped electrode 13' arranged between the anode '14 and the incandescentz-"eatliode 15 of a discharge gap. 1 The cathode is heated by. a heating battery 16. The circuit of the discharge gap leads from a battery 17 through a non-inductive high resistance 18.

An'auxiliary potential from a battery 19 is applied to the grid-shaped auxiliary elece 13'. 1 The fluctuations of potential that arise in the discharge ga when the auxiliary electrade-13" is osci ate'd' are communicated drawing I the through a conductor 20 to the grid or controlling electrode 22 of a thermionic valve 21 or amplifier. The thermionic valve 21 comprises, as well known, an incandescent cathode 23 which is heated by a heating battery 24 and an anode 25. Connected in the anode circuit, which receives current from a battery 28, is a high 0l1I Il1C resistance 26. The anode 25 is connected by a wire 27 'to the metal sieve or grid 9 so that the fluctuating potentials of the anode 21 are-imparted to the grid 9.

It is particularly important to maintain the pressure in the steam boiler as uniform as possible. This is accomplished by an electric regulator which comprises a mercury pressure gauge 29. When the steam pressure raises to a certain point the .mercury.,30 closes an electric contact in a circuit containing a relay which regulates the heating current.

The scope of the invention is not limited to the use of a steam electrifying device of the Armstrong type for it will also be feasible to em loy an arrangement in which the electrification of the water vapor or any other suitable fluid is not efiected by friction, but 'by influence.

We claim:-

1. In a device for reproducing sounds, means for producing a continuous current of gas' or steam, and means in the path of saidcurrent for producing an electric field of changing intensity for controlling said current. a

2. In .a' device for reproducing sounds means for producin a continuous current 0 gas or steam, a, per orated metal body in the path of :said current, means for electrically charging said gas or steam and nieans to vary said chargin in rhythm to sound waves.

3. In a device or reproducing sounds, an electric heating means for converting water into a current of steam, means for electrically charging said current, and" means for producing an electric field of changing in-- tensity for controlling said flow.

.4. In a device for reproducing sounds, an electric heating means for converting water into a current of steam, means for electrically charging said current,.a perforated metal body in the path of said current, and means for variably electrically charging said body in the rhythm of sound waves.

5. In a device for reproducing sounds, an electric steam generator, a perforated metal body, a channelled body including a condensed water container for conducting the steam 'to said erforated body, means for c'onductin con ensed water from said container bac to the. steam generator, means for electrically charging the current of steam, and means for variably electrically charging said perforated metal body in the rhythm of sound waves.

6. In a deyice for reproducing sounds, an eontainerback to the steam generator, means 10 electric steam generator, aperforated metal for electrically charging the current of body, a nozzle leadingto said perforated steam and means for variabl electrically. body, a channelled body including a conchargmg said perforated meta body in the 5 densed water container, a' body with a narrhythm of sound waves.

. i ow serpentine passage formed therein for In testimony that. We claim the foregoing 1 conducting steam from said channelled body as our invention, We have signed our names. to said nozzle and erfora'ted body, means OTTO BOTHE.

for conducting condlansed water from said LUDWIG SOHIFF. 

